Edit*
I see so many people ingame asking wich key to use for what etc..

Seriously people: SET YOUR KEYBINDS BEFORE PLAYING..

Oh didnt notice my caps was on..

However! I got this too. Thing is, the tutorial still said Middle Mouse (the default) even though I'd set it to Mouse Wheel Up (I use this for melee in a few games). On top of that, because I'd forced AA (better than game AA by a mile), the controls screen was not showing up for me so I couldn't check what alt fire was (not realizing that alt fire and melee were on the same function).